This remarkable and beautiful animal lives in my refugium *entirely* by himself (with only amphipods and copepods and other tiny dentrivores, which he does not bother).
They cannot be kept with other animals because they are highly predatory; just ask anyone who has ever spent weeks attempting to catch a mantis in their reef tank or mysteriously lost expensive fish to these fierce predators. To most hobbyists, they are considered pests (that hitchhike in on live rock), much to the dismay of the aquarium owner who may try in vain to trap them and keep them from destroying the entire reef. However, they are actually well sought-after by mantis fans, myself included, since they have such beauty, cool behavior,
and are otherwise very difficult to obtain both online and from stores. Mantis are classified into two general groups: "smashers" that club their prey with great force, and "spearers" that have sharp appendages that literally skewer their prey. O. scyllarus, shown above, is a smasher, and I have seen him kill animals his own weight or more (including one poor crayfish with a rather hard shell, that he just pummeled to death). Mine is only about 2" long right now, just a juvenile, but I'm sure will grow well on the diet I'm giving it (1 small shrimp every other day on a stick, being very careful to watch my own fingers).